The First Minister faced a barrage of questions over a botched contract to build two ferries at the Ferguson shipyard in Port Glasgow as she launched her party’s local election manifesto in nearby Greenock.
The vessels, the Glen Sannox and the as-yet-unnamed hull 802, are at least £150 million over budget and five years late.
Speaking at the Beacon Arts Centre, Ms Sturgeon insisted the ferries “are going to sail” and she deeply regretted the delays.
A recent report from Audit Scotland found there was “insufficient documentary evidence” to explain why the contract was given to the Ferguson shipyard, which has since been nationalised, without a full refund guarantee.
Scottish Government officials later said a “thorough search” had been conducted and the documentation could not be located.
Richard Leonard, convener of Holyrood’s public audit committee, suggested the government’s actions were not consistent with the Public Finance and Accountability Act.
Scotland’s auditor general Stephen Boyle told the committee there was “clearly a frustration from us that we weren’t able to review what we would consider to be all the relevant evidence”.
He said: “Our judgment is not that evidence has been withheld from us during the course of our audit work, but rather that an important piece of documentary evidence wasn’t prepared to arrive at the judgment that ministers arrived at – to accept the scale of risk so unusual in the scale of this contract and contrary to the advice of the public body (Caledonian Maritime Assets Limited) which oversees the contract.”
Asked if the missing paperwork was a result of incompetence or a cover up, Ms Sturgeon said: "There is no cover up. There is clearly a key point of decision making that has not been recorded in the way it should have been.
"That is regrettable, but there is no cover up around this.
"I didn't have the opportunity to listen to all of the auditor general's session yesterday in full, but I think - and correct me if I'm quoting him wrongly here - but I think I saw it reported that there was no suggestion from the auditor general that information had been withheld from Audit Scotland.
"It was simply that this particular piece of written evidence, this particular decision hadn't been recorded.
"That is regrettable - I'm not trying to diminish the importance of that.
"But anybody can go on to the Scottish Government website and look at the sheer quantum of paperwork recording our decisions around this issue, other than that.
"Beyond that, obviously the Public Audit Committee will continue to look at this.
"If they ask me to give evidence I will do that and I will seek to answer all of their questions to the very best of my ability."
The First Minister said the government “will of course reflect on any lessons we need to learn”.
Asked if there should be a full public inquiry into the debacle, she said nothing is being ruled out, adding: “But I think we’ve got to allow the public audit committee to do its work and then see, at the end of that, whether a fuller inquiry would still be merited or not at that stage.”
Scottish Conservative transport spokesman Graham Simpson said: “It is completely unacceptable for the SNP to claim they can’t find the paperwork explaining why ministers ignored CMAL’s [Caledonian Maritime Assets Limited’s] warnings about the dangers of awarding the contract to Ferguson Marine.
“In this day and age, it’s almost inconceivable there is not an electronic trail of how this fateful decision was made, even if there is no paper copy.”
He added: “It’s clearer than ever we need a public inquiry to get to the bottom of this murky affair.”